Type III — low-pressure appliancesDifficulty 4/5
What is the preferred method of pressurising a low-pressure system for a leak test?
- ACompressed air through a filter-drier, with nitrogen used only for large chillers
- BOxygen through a pressure regulator, with a relief valve fitted to the test line
- CControlled hot water or a built-in heating device, with nitrogen as the fallback
- DNitrogen through a pressure regulator, with controlled hot water as the fallback
Show answer and rationale
Correct: C. Heat is preferred because it needs no purging afterwards. Section 82.156(a)(1)(ii) makes the same distinction for non-major repairs, barring methods requiring subsequent purging where the refrigerant boils at or below 85 degrees Fahrenheit.
- D — The order is reversed; nitrogen is the fallback precisely because it must be purged.
- A — Compressed air introduces moisture and is not an approved leak-test pressurisation method.
- B — Oxygen must never be used to pressurise a system containing refrigerant oil.